A US inmate has been sentenced to 24 additional years behind bars after murdering his cellmate, the paedophile who abused his sister – in an act of bloody revenge.

An administrative error saw 26-year-old Shane Goldsby assigned to the same cell as Robert Munger before the fatal beating in June 2020.

Munger, 70, was serving a 43-year sentence at the Airway Heights prison in Washington State for child molestation and child pornography offences.

Local news station KHQ reported that Goldsby discovered that his younger sister was one of Munger’s victims.

“I had so much stuff going on in my head,’ he told the station. “I wasn’t stable at that point. I wasn’t. I was getting to that point, because [Munger] kept wanting to give me details about what happened, what he did – about the photos and the videos of him doing this stuff. It was building up.”

Goldsby said he couldn’t believe that he had been assigned to the same cell and made a request to the authorities that he be moved, which was ignored.

“I’m completely feeling like this is what they wanted to happen,” he said.

“I was in shock,” he added. “I was like, ‘what the f***?’… This stuff doesn’t happen. You’re talking the same institution, the same unit, the same pod in the same cell as this dude. That’s like hitting the jackpot in the casino seven times.” 

“They put me in a position that I shouldn’t even be in. This shouldn’t have happened, at all. You’re talking about this dude, who did some sick twisted things to my little sis. My family. My blood. My life. And you want to put me face-to-face with this dude?” Goldsby told KHQ.

Goldsby eventually snapped, attacking the older man in a common area in the jail.

Court documents reveal what happened next, showing how Goldsby hit “Munger in the face and head area about 14 times, [stomped] on his head at least four times and [kicked] a couple more times before walking away and being taken into custody.” He died three days later.

The Washington Department of Corrections has policies to prevent connected inmates being assigned together but reportedly missed the connection in this case because Goldsby and his sister have different last names.

“There was no clear indication in the documentation regularly reviewed for housing assignments that there was a potential conflict,” DoC spokeswoman Janelle Guthrie told the Spokesman-Review newspaper.

“You put me in the same cell as this dude,” Goldsby said. “I feel set up. I’m the victim.”

At his sentencing last week, Goldsby was too emotional to read a statement and his lawyer spoke on his behalf.

“I’m ashamed of my actions, I was put into a situation that I don’t wish on nobody,” she said on Goldsby’s behalf. “I got a lot of fixing to do.”

In addition to the additional 22 years, Goldsby must also pay restitution to Munger’s family.

“I cannot imagine what it would be like to lose a loved one in this kind of way,” Goldsby said through his lawyer.

“To his wife and his whole family I apologise. I am so sorry and I hope you are able to heal from what I caused.”